1. Field of the Invention
The present invention relates to a method and an apparatus for driving a liquid crystal display device and more particularly to a method and an apparatus for driving a liquid crystal display device capable of improving the contrast of a display image.
2. Description of the Related Art
A liquid crystal display displays pictures by adjusting the light transmittance of liquid crystal cells in response to a video signal. The liquid crystal display is an active matrix type having a switching device in each cell and may be used as the display apparatus for a computer monitor, an office automation apparatus, and a cellular phone. A thin film transistor (hereinafter referred to as a “TFT”) is typically used as a switching device in an active matrix liquid crystal display.
FIG. 1 schematically illustrates a driving apparatus of the liquid crystal display according to the related art. Referring to FIG. 1, the driving apparatus of the liquid crystal display of the related art comprises a liquid crystal panel 2, wherein m×n liquid crystal cells are arranged in a matrix, and wherein the number of data lines D1 to Dm is m and the number of gate lines G1 to Gn is n. The data and gate lines cross, and a TFT is formed at the interconnection. The driving apparatus also includes a data driver 4 that supplies a data signal to the data lines D1 to Dm of the liquid crystal panel 2, a gate driver 6 that supplies a scan signal to the gate lines G1 to Gn, a gamma voltage supplier 8 supplies a gamma voltage to the data driver 4, a timing controller 10 that controls the data driver 4 and the gate driver 6 by using a synchronization signal provided from a system 20, a DC/DC converter 14 that generates voltages supplied to the liquid crystal panel 2 by using a voltage supplied from a power supply 12, and an inverter 16 that drives a backlight 18.
The system 20 supplies to the timing controller 10 vertical/horizontal synchronization signal Vsync, Hsync, a clock signal DCLK, a data enable signal DE, and R, G and B data signals.
The liquid crystal panel 2 comprises a plurality of liquid crystal cells Clc arranged in a matrix created by the interconnection of the data lines D1 to Dm and the gate lines G1 to Gn. The TFTs in each liquid crystal cell Clc supplies the liquid crystal cell Clc the data signal supplied from the data lines D1 to Dm in response to the scan signal supplied from the gate line G. Further, each liquid crystal cell Clc has a storage capacitor Cst. The storage capacitor Cst is formed between a pixel electrode of the liquid crystal cell Clc and a previous gate line or may be formed between the pixel electrode of the liquid crystal cell Clc and a common electrode line and thereby maintains a voltage applied to the liquid crystal cell Clc.
The gamma voltage supplier 8 provides a plurality of gamma voltages to the data driver 4. The data driver 4 converts R, G, and B digital video data signals into an analog gamma voltage (data signal) corresponding to a gray scale value in response to a control signal Cs from the timing controller 10 and supplies this analog gamma voltage to the data lines D1 to Dm.
The gate driver 6 sequentially supplies a scan pulse to the gate lines G1 to Gn in response to the control signal CS from the timing controller 10 and selects a horizontal line of the liquid crystal panel 2 to which the data signal is supplied.
The timing controller 10 generates the control signal CS to control the gate driver 6 and the data driver 4 by using the vertical/horizontal synchronization signals Vsync and Hsync and the clock signal DCLK received from the system 20. The control signal CS that controls the gate driver 6 includes a gate start pulse GSP, a gate shift clock GSC, and a gate output enable GOE. The control signal CS that controls the data driver 4 includes a source start pulse GSP, a source shift clock SSC, a source output enable SOC, and a polarity signal POL. The timing controller 10 rearranges the R, G, and B data supplied from the system 20 to supply it to the data driver 4.
The DC/DC converter 14 increases or decreases the voltage level of a 3.3 V signal received from the power supply 12 and generates a voltage to be supplied to the liquid crystal panel 2. The DC/DC converter 14 generates a gamma reference voltage, a gate high voltage VGH, a gate low voltage VGL, and a common voltage Vcom.
The inverter 16 supplies a drive voltage (or a drive current) to drive the backlight 18. The backlight 18 generates a light level corresponding to the drive voltage (or the drive current) supplied by the inverter 16 to the liquid crystal panel 2.
In order to display dynamic pictures on the liquid crystal panel 2, it is desirable that the contrast should be as great as possible. However, there is not a method available that is capable of extending the contrast inherent in the display data on the liquid crystal display of the related art, and thus it is difficult to display dynamic pictures. Further in the related art, the backlight 18 of the liquid crystal display constantly and uniformly radiates irrespective of the data. If the backlight 18 constantly and uniformly radiates irrespective of the data, it is difficult to display dynamic and vivid pictures in the liquid crystal panel 2.